Calcium-activated potassium channels and voltage-gated calcium channels will be studied by a combination of biochemical, biophysical, and electrophysiological techniques. The long term goals of this project is to understand the molecular mechanisms of regulation of ion channel activity in presynaptic nerve terminals from mammalian brain. Two specific examples of such regulation will be examined using measurements of ion flux in isolated presynaptic nerve terminals from rat brain, and the planar lipid bilayer technique: A. The molecular mechanisms underlying the block of presynaptic calcium activated potassium channels by clinically important neuroleptics, heavy metal ions, and protein kinase will be examined by reconstituting fragments of nerve terminal membranes into planar lipid bilayers, thus affording the opportunity to study the interaction of these neuromodulators with single potassium channel molecules in great detail. B. The biochemical link between occupancy of presynaptic opioid receptors and the block of calcium channels will be examined in intact nerve terminals and on the single channel level in the planar lipid bilayer. It is anticipated that these studies will generate new information about the molecular details underlying the regulation of presynaptic excitibility and synaptic transfer.